U.S. Pat. No. 2,715,022 issued in 1955 to Krotz discloses a typical spring suspension system for a vehicle supported over ground by a wheel axle. In this suspension unit attached on either side to the beams of a truck frame, there is provided on each side of the vehicle axle 11 a pair of pivotal rubber torsion connections 21, 36 which extend longitudinally of the vehicle in laterally spaced fashion. Each pair of rubber connections 21, 36 are interconnected by a pivotal arm 29, wherein the arms and the axle have a statically loaded position relative to the vehicle frame in which the arms extend horizontally and the rubber bodies are distorted in radial compression by forces acting in a direction to impart compressive stress in each arm. These arms are movable arcuately to another position at which the distortion of the rubber is relieved.
The stability of the vehicle provided with such a suspension system could be improved. Indeed, in this and other prior art patents, the suspension use solely torsion bars as the spring-loaded suspension system. Such torsion members are deemed by the present inventor to be inefficient.